I like the looks of that, but I don't see the need. I've concluded that for powering my tadpole I'll go with a Currie type drive on each front wheel, powered by a small portable generator driven by a 2 stroke (perhaps 4 stroke) engine, a single deep cycle battery for load smoothing.
Put 350 watts of power on each front wheel, set up to freewhel when not in use, and go with a Shimano multi-speed hub at the rear, driven conventionally. The really lovely part of doing the system I envision is when I need silent running, I can shut down the generator. Until I can afford that, I'll be pedalling.